Industry experiences with immune-mediated findings in biotherapeutic nonclinical toxicology studies.

With the growth of monoclonal antibodies and other proteins as major modalities in the pharmaceutical industry, there has been an increase in pharmacology and toxicity testing of biotherapeutics in animals. Animals frequently mount an immune response to human therapeutic proteins. This can result in asymptomatic anti-drug antibody formation, immune complexes that affect drug disposition and/or organ function such as kidney, cytokine release responses, fatal hypersensitivity, or a range of reactions in between. In addition, an increasing number of oncology therapeutics are being developed that enhance or directly stimulate immune responses by a variety of mechanisms, which could increase the risk of autoreactivity and an autoimmune-like syndrome in animals and humans. When evaluating the risk of biotherapeutics prior to entering the clinic, the nonclinical safety data may include any of these responses and it is critical to understand whether they represent a safety liability for humans. The DruSafe Leadership group of the IQ Consortium conducted a survey of industry to understand sponsors' experiences with these immune reactions in nonclinical studies related to both immunogenicity and pharmacologically-mediated immune perturbations. The survey covered what pathways were affected, how the immune responses were presented, how the company and health authorities interpreted the data and whether the immune responses were observed in the clinic. Additionally, the survey gathered information on association of these findings with anti-drug antibodies as well as sponsor's use of immunogenicity predictive tools. The data suggests that the ability of a biotherapeutic to activate the immune system, intended or not, plays a significant role on characteristics of the response and whether theys are translatable.

In vitro assays supporting the safety assessment of immunomodulatory monoclonal antibodies.

Many monoclonal antibodies (mAbs) licensed for human use or in clinical development for cancer and autoimmune disease directly interact with the immune system. These immunomodulatory mAbs have an inherent risk of adverse immune-mediated drug reactions, including infusion reactions, cytokine storms, immunosuppression and autoimmunity. A thorough understanding of the potential for immunotoxicity of a mAb is required to support administration to humans. This review will highlight the key role of in vitro assays in defining the immunopharmacology, immunotoxicity and immunogenicity of mAbs. A wide range of in vitro tests with multiple formats of different complexity can be utilized to characterize i) the antibody-binding domains of the mAb, such as on-target binding and downstream pharmacological effects (e.g. immunosuppression, immune activation, cytokine release) in both humans and animal species used for toxicology studies and off-target binding; ii) Fc-dependent effects such as Fc-mediated cellular activation (e.g. of leukocytes, platelets) and cytokine release, complement activation; and iii) product-related factors (sequence, physical-chemical properties and impurities) that can impact both pharmacological activity and immunogenicity potential of a mAb. These assays can be crucial to the selection of mAbs with an optimum balance of safety and efficacy, in defining whether a mAb is a high risk molecule, and together with animal data, can inform human safe starting doses and escalation schemes.

Safety and immunotoxicity assessment of immunomodulatory monoclonal antibodies.

Most therapeutic monoclonal antibodies (mAbs) licensed for human use or in clinical development are indicated for treatment of patients with cancer and inflammatory/autoimmune disease and as such, are designed to directly interact with the immune system. A major hurdle for the development and early clinical investigation of many of these immunomodulatory mAbs is their inherent risk for adverse immune-mediated drug reactions in humans such as infusion reactions, cytokine storms, immunosuppression and autoimmunity. A thorough understanding of the immunopharmacology of a mAb in humans and animals is required to both anticipate the clinical risk of adverse immunotoxicological events and to select a safe starting dose for first-in-human (FIH) clinical studies. This review summarizes the most common adverse immunotoxicological events occurring in humans with immunomodulatory mAbs and outlines non-clinical strategies to define their immunopharmacology and assess their immunotoxic potential, as well as reduce the risk of immunotoxicity through rational mAb design. Tests to assess the relative risk of mAb candidates for cytokine release syndrome, innate immune system (dendritic cell) activation and immunogenicity in humans are also described. The importance of selecting a relevant and sensitive toxicity species for human safety assessment in which the immunopharmacology of the mAb is similar to that expected in humans is highlighted, as is the importance of understanding the limitations of the species selected for human safety assessment and supplementation of in vivo safety assessment with appropriate in vitro human assays. A tiered approach to assess effects on immune status, immune function and risk of infection and cancer, governed by the mechanism of action and structural features of the mAb, is described. Finally, the use of immunopharmacology and immunotoxicity data in determining a minimum anticipated biologic effect Level (MABEL) and in the selection of safe human starting dose is discussed.

Prostate stem cell antigen: Identification of immunogenic peptides and assessment of reactive CD8+ T cells in prostate cancer patients.

Identification of TAAs recognized by CD8(+) CTLs paved the way for new concepts in cancer therapy. In view of the heterogeneity of tumors and their diverse escape mechanisms, CTL-based cancer therapy largely depends on an appropriate number of TAAs. In prostate cancer, the number of antigens defined as suitable targets of CTLs remains rather limited. PSCA is widely distributed in prostate cancer. In this report, we define immunogenic peptides of PSCA which are recognized by circulating CD8(+) T cells from prostate cancer patients and able to activate CTLs in vitro. Screening the amino acid sequence of PSCA for peptides containing a binding motif for HLA-A*0201 resulted in 8 candidate peptides. Specificity and affinity of peptide binding were verified in a competition assay. Frequencies of CD8(+) T lymphocytes reactive against selected epitopes were determined in the blood of prostate cancer patients using the ELISPOT assay. Increased frequencies were revealed for CD8(+) T cells recognizing the peptides ALQPGTALL and AILALLPAL. CTLs from prostate cancer patients were raised against these 2 peptides in vitro when presented by autologous DCs. They specifically recognized peptide-pulsed T2 target cells and prostate cancer cells that were HLA-A*0201- and PSCA-positive, indicating that these peptides were naturally generated by tumor cells. These data suggest that PSCA is a promising target for the immunotherapy of prostate cancer.